1. Technical Field
The present invention relates to a light source device, an image display device, and a light amount correction method.
2. Related Art
In recent years, a laser scanning display that displays an image by raster scanning beam-shaped light, such as a laser beam, onto a projected surface has been drawing attention as one type of an image display device. Such a laser scanning display is characterized in that the contrast is very high because a completely black color can be expressed by stopping supply of a laser beam, the color purity is high because a laser beam has a single wavelength, and a laser beam is easily shaped (easily focused) because the laser beam has high coherence compared with a projector using a liquid crystal light valve, for example. Accordingly, the laser scanning display is expected as a high-quality display that realizes high contrast, high color reproducibility, and high resolution.
As a laser light source of the laser scanning display, a semiconductor laser element, such as a laser diode, is mainly used. However, since a laser characteristic of the semiconductor laser element changes due to a temperature change or aging deterioration, for example, it is necessary to correct the laser light amount in order to obtain desired image brightness.
For example, JP-A-7-147446 discloses a technique in which two or more points of a bias current value of a semiconductor laser element are changed, light emission power of the semiconductor laser element is detected by a light receiving power detecting unit, and a change in quantum efficiency and threshold current value of the semiconductor laser element is detected such that a DC bias current of the semiconductor laser element is set in a bias current control unit, and a level of a laser output is held constant by setting a pulse current, which corresponds to the change in quantum efficiency, in a pulse current control unit. In addition, JP-A-2003-91853 discloses a technique of adjusting an output level of a laser light source by automatically calculating the relational expression between the detected light amount of the laser light source and a set value of a light output and setting data of the relational expression in an optical recording medium drive device.
Thus, in the case of correcting the laser light amount according to a change in laser characteristic resulting from the temperature change or aging deterioration, it is preferable to perform light amount correction in real time according to the change in laser characteristic while actually operating the device in order to further increase the correction accuracy. However, the means therefor is not proposed in the above known techniques.